Focusing device.



E. w. DAVIS. l Focusmc DEVICE. APPLICATION FILED MAR. I6. 1911.

Patented Aug. 27, 1918.v

wTNESSE/S of focus is desirable.

UNITED sTATEs PATENT oEE-roE.

ERNEST W. DAVIS, OF CHICAGO, ILLINOIS.

FOCUSING- DEVICE.

cago, in the coun'ty of Cook and State of' Illinois, have invented a new and useful Improvement in Focusing Devices, of which the following is a full, clear, and exact description.

My invention relates to focusing devices as applied to cameras and more particularly to the focusing devices of moving picture cameras.

The object of this invention is to provide means whereby a lens. may be accurately fcusedfto throw a sharp image on a receiving surface, such, for instance, as a moving picture film, where extreme precision The above named object is accomplished by vproviding means for viewing the image on the photographic lm from the front side instead of from the back. In prior devices, where.the image on the film is viewed through the film itself, the illumination .is usually insuflicient for good -focusing' and the image is somewhat blurred by diffusion, as also occurs when ground glass or /ground Lillian ,is used to replace the photographic This invention comprises a reecting surface, preferably a prism, located in front sis' piece is advantageous for accurate focusing of the film and arranged to reect the image on the emulsion through an aperture in the camera case, so that 'the operator may view l the image as it. actuallyfexists where .the` photographicv exposure is made.

A suitable eye piece vmay be used for 'ex cluding external sources of light while the` operator is viewing the image.

A lmagnifying lens located in the eye Aand may be made integral with the prism, if

Aso desired.

A lspecific embodiment of this inventicin'is illlllistll'ated 1n the. accompanying. drawing in w 1c I4`igure1iseJ sectional plan showing the Y position ofthe prism relative to the aperture plate and camera lens.

Fig. 2 is an elevation of the camera case showing the aperture in which the eyepiece containing the prismmay be inserted.

Fig. 3 is a sectional elevation through the eyepiece holder showing the arrangement of the slide qfor excluding the light when' the eyepiece is withdrawn.

Patented Aug. 27, 1918.

Application led March 16, 1917. Serial No. 155,196.

Referring to Fig. 1,I a moving picture camera lens 4, is provided .with a lens barrel 14, and a sleeve 5, through which the lens barrel 14 may be moved longitudinally. The aperture plate 6, is arranged to carry the photographic film 7, which may be intermittently advanced by any of they well known devices used for that purpose.

The camera case 8, has an opening to receive the eyepiece holder 9, which is arranged to hold the eyepiece 10, in the posiL tion indicated. The eyepiece 10, contains a prism 11, having a reflecting surface 12, arranged to reiect the image on the film 7, through the eyepiece 10. A convex lens 13, integra-l with the prism 11, enlarges the image and permits focusing with the operators eye pressed tightly against the rim 15, which is curved to fit the eye thereby excluding external light.

In operation the operator looks through the lens 13, and prism 11, and sees the image on the film 7 which is produced by the lens 4. He then moves the lens barrel 14, in or out until the picture 'is accurately focused. The eye-piece 10, is then removed, leaving the eyepiece holder 9, empty as shown in Fig. 3, when the slide 16, may be lowered by means of the knob 17, thereby excluding light from the camera, which is then in focus and ready for operation. Y It has beendetermined by practice that the prism 11, may be inserted to the amount shown in Fig. 1, z'. e.to the center line of the lens 4, without greatly diminishing the apparent.illuminatlon of any part of the image.

Any further insertion however, diminished the illumination quite rapidly.

I am aware that prior to my invention moving picture cameras have been constructed, in which a prism is interposed between the lens and the lm, for ,the purpose Qfreecting the-rays of light from the lens onto'a. ixedground glass, but I am not aware that a prism has ever been arranged to reiect the image from the front of the sensitive film. through an aperture in the camera case.

I claim:

1. In combination, a lens adapted to produce an image, a receiving surface arranged to receive said image, a light excluding casing having an aperture therein and surrounding the space between saidy lens and said receiving surface, and a reflectin sur-` face interposed between said lensan said receiving surface and arranged to reflect said image through said aperture.

2. In combination, a lens adapted to produce an image, a receiving surface arranged to receive said image, an eyepiece, and a reliecting surface interposed between said lens and said receiving surface and arranged to reflect said image through said eyepiece.

3. In combination, a camera lens arranged to produce an image on a receiving surface,

a magnifying lens, and a reflecting surface v interposed between said camera lens and said receiving surface and arranged to reflect `said image through said magnifying lens. l

4:. In combination, a camera lens arranged to produce an image on a receiving surface, a prism having a reflecting surface, and a magnifying lens, said prism being interposed between said camera lens and said receiving surface and arranged to reflect said image through said magnifying lefns.

5. In combination, a camera lens ar- Asaid magnlfying 6. In a focusing device, the combination face, a magnifying lens integral with said 25 prism, said prism beingpinterposed between said camera lens and said receiving surface and arranged to reflect said image through lens.

with a photographic film and a lens arranged to produce an image on said lm, of a light excluding casing having an aperture therein and surrounding the space between said lens and said film, and a single reflecting surface forward of said film and arranged to reflect the image on said film through said aperture.

In testimony WhereoztI aiix my signature in the presence of two witnesses.

ERNEST W. DAVIS. Witnesses:

A.. V. DOUGLAss, HENRY E. WISTEN. 

